Android实现悬浮可拖拽的Button

public class DraggingButton extends android.support.v7.widget.AppCompatButton {   private int lastX = 0;  private int lastY = 0;  private int beginX = 0;  private int beginY = 0;   private int screenWidth = 720;  private int screenHeight = 1280;    public DraggingButton(Context context) {    this(context, null);  }   public DraggingButton(Context context, @Nullable AttributeSet attrs) {    this(context, attrs, 0);  }   public DraggingButton(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {    super(context, attrs, defStyleAttr);     initData(context);  }   private void initData(Context context){    WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);    DisplayMetrics dm = new DisplayMetrics();    wm.getDefaultDisplay().getMetrics(dm);    screenWidth = dm.widthPixels;    screenHeight = dm.heightPixels;  }   @Override  public boolean onTouchEvent(MotionEvent event)  {     switch (event.getAction())    {      case MotionEvent.ACTION_DOWN:        lastX = (int) event.getRawX();   // 触摸点与屏幕左边的距离        lastY = (int) event.getRawY();   // 触摸点与屏幕上边的距离        beginX = lastX;        beginY = lastY;        break;      case MotionEvent.ACTION_MOVE:         int dx =(int)event.getRawX() - lastX;    // x轴拖动的绝对距离        int dy =(int)event.getRawY() - lastY;    // y轴拖动的绝对距离         // getLeft(): 子View的左边界到父View的左边界的距离, getRight():子View的右边界到父View的左边界的距离        // 如下几个数据表示view应该在布局中的位置        int left = getLeft() + dx;        int top = getTop() + dy;        int right = getRight() + dx;        int bottom = getBottom() + dy;        if(left < 0){          left = 0;          right = left + getWidth();        }        if(right > screenWidth){          right = screenWidth;          left = right - getWidth();        }        if(top < 0){          top = 0;          bottom = top + getHeight();        }        if(bottom>screenHeight){          bottom = screenHeight;          top = bottom - getHeight();        }        layout(left, top, right, bottom);        lastX = (int) event.getRawX();        lastY = (int) event.getRawY();        break;      case MotionEvent.ACTION_UP:        // 解决拖拽的时候松手点击事件触发        if (Math.abs(lastX - beginX) < 10 && Math.abs(lastY - beginY) < 10){          return super.onTouchEvent(event);        }else{          setPressed(false);          return true;        }      default:        break;    }    return super.onTouchEvent(event);  }}

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  xmlns:app="http://schemas.android.com/apk/res-auto"  xmlns:tools="http://schemas.android.com/tools"  android:layout_width="match_parent"  android:layout_height="match_parent"  android:orientation="vertical">  <com.android.study.example.uidemo.dragging.DraggingButton    android:id="@+id/tv_dragging"    android:layout_width="80dp"    android:layout_height="80dp"    android:gravity="center"    android:background="@drawable/drag_button_bg"    android:layout_margin="20dp"    android:padding="10dp"    android:text="悬浮/n按钮1"    android:textSize="15sp"    android:layout_gravity="right"    android:textColor="#ffffff"/></LinearLayout>

<?xml version="1.0" encoding="utf-8"?><selector xmlns:android="http://schemas.android.com/apk/res/android">  <item android:state_pressed="true">    <shape android:shape="oval">      <!--填充颜色-->      <solid android:color="#bf39b500" />      <!--描边-->      <stroke android:width="2dp" android:color="#bf39b500" />    </shape>  </item>  <item>    <shape android:shape="oval">      <!--填充颜色-->      <solid android:color="#ff8bc34a" />      <!--描边-->      <stroke android:width="2dp" android:color="#bf39b500"/>    </shape>  </item></selector>

private DraggingButton mDraggintView;mDraggintView = (DraggingButton) findViewById(R.id.tv_dragging);  mDraggintView.setOnClickListener(new View.OnClickListener() {   @Override   public void onClick(View v) {    Toast.makeText(FloatingActionBtnTestActivity.this, "click", Toast.LENGTH_SHORT).show();   }  });